/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package com.sun.org.apache.xml.internal.security.utils;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.math.BigInteger;

import com.sun.org.apache.xml.internal.security.exceptions.Base64DecodingException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.Text;

/**
 * Implementation of MIME's Base64 encoding and decoding conversions.
 * Optimized code. (raw version taken from oreilly.jonathan.util,
 * and currently org.apache.xerces.ds.util.Base64)
 *
 * @author Raul Benito(Of the xerces copy, and little adaptations).
 * @author Anli Shundi
 * @author Christian Geuer-Pollmann
 * @see <A HREF="ftp://ftp.isi.edu/in-notes/rfc2045.txt">RFC 2045</A>
 * @see com.sun.org.apache.xml.internal.security.transforms.implementations.TransformBase64Decode
 */
public class Base64 {

  /**
   * Field BASE64DEFAULTLENGTH
   */
  public static final int BASE64DEFAULTLENGTH = 76;

  private static final int BASELENGTH = 255;
  private static final int LOOKUPLENGTH = 64;
  private static final int TWENTYFOURBITGROUP = 24;
  private static final int EIGHTBIT = 8;
  private static final int SIXTEENBIT = 16;
  private static final int FOURBYTE = 4;
  private static final int SIGN = -128;
  private static final char PAD = '=';
  private static final byte[] base64Alphabet = new byte[BASELENGTH];
  private static final char[] lookUpBase64Alphabet = new char[LOOKUPLENGTH];

  static {
    for (int i = 0; i < BASELENGTH; i++) {
      base64Alphabet[i] = -1;
    }
    for (int i = 'Z'; i >= 'A'; i--) {
      base64Alphabet[i] = (byte) (i - 'A');
    }
    for (int i = 'z'; i >= 'a'; i--) {
      base64Alphabet[i] = (byte) (i - 'a' + 26);
    }

    for (int i = '9'; i >= '0'; i--) {
      base64Alphabet[i] = (byte) (i - '0' + 52);
    }

    base64Alphabet['+'] = 62;
    base64Alphabet['/'] = 63;

    for (int i = 0; i <= 25; i++) {
      lookUpBase64Alphabet[i] = (char) ('A' + i);
    }

    for (int i = 26, j = 0; i <= 51; i++, j++) {
      lookUpBase64Alphabet[i] = (char) ('a' + j);
    }

    for (int i = 52, j = 0; i <= 61; i++, j++) {
      lookUpBase64Alphabet[i] = (char) ('0' + j);
    }
    lookUpBase64Alphabet[62] = '+';
    lookUpBase64Alphabet[63] = '/';
  }

  private Base64() {
    // we don't allow instantiation
  }

  /**
   * Returns a byte-array representation of a <code>{@link BigInteger}<code>.
   * No sign-bit is output.
   *
   * <b>N.B.:</B> <code>{@link BigInteger}<code>'s toByteArray
   * returns eventually longer arrays because of the leading sign-bit.
   *
   * @param big <code>BigInteger<code> to be converted
   * @param bitlen <code>int<code> the desired length in bits of the representation
   * @return a byte array with <code>bitlen</code> bits of <code>big</code>
   */
  static final byte[] getBytes(BigInteger big, int bitlen) {

    //round bitlen
    bitlen = ((bitlen + 7) >> 3) << 3;

    if (bitlen < big.bitLength()) {
      throw new IllegalArgumentException(I18n.translate("utils.Base64.IllegalBitlength"));
    }

    byte[] bigBytes = big.toByteArray();

    if (((big.bitLength() % 8) != 0)
        && (((big.bitLength() / 8) + 1) == (bitlen / 8))) {
      return bigBytes;
    }

    // some copying needed
    int startSrc = 0;    // no need to skip anything
    int bigLen = bigBytes.length;    //valid length of the string

    if ((big.bitLength() % 8) == 0) {    // correct values
      startSrc = 1;    // skip sign bit

      bigLen--;    // valid length of the string
    }

    int startDst = bitlen / 8 - bigLen;    //pad with leading nulls
    byte[] resizedBytes = new byte[bitlen / 8];

    System.arraycopy(bigBytes, startSrc, resizedBytes, startDst, bigLen);

    return resizedBytes;
  }

  /**
   * Encode in Base64 the given <code>{@link BigInteger}<code>.
   *
   * @return String with Base64 encoding
   */
  public static final String encode(BigInteger big) {
    return encode(getBytes(big, big.bitLength()));
  }

  /**
   * Returns a byte-array representation of a <code>{@link BigInteger}<code>.
   * No sign-bit is output.
   *
   * <b>N.B.:</B> <code>{@link BigInteger}<code>'s toByteArray
   * returns eventually longer arrays because of the leading sign-bit.
   *
   * @param big <code>BigInteger<code> to be converted
   * @param bitlen <code>int<code> the desired length in bits of the representation
   * @return a byte array with <code>bitlen</code> bits of <code>big</code>
   */
  public static final byte[] encode(BigInteger big, int bitlen) {

    //round bitlen
    bitlen = ((bitlen + 7) >> 3) << 3;

    if (bitlen < big.bitLength()) {
      throw new IllegalArgumentException(I18n.translate("utils.Base64.IllegalBitlength"));
    }

    byte[] bigBytes = big.toByteArray();

    if (((big.bitLength() % 8) != 0)
        && (((big.bitLength() / 8) + 1) == (bitlen / 8))) {
      return bigBytes;
    }

    // some copying needed
    int startSrc = 0;    // no need to skip anything
    int bigLen = bigBytes.length;    //valid length of the string

    if ((big.bitLength() % 8) == 0) {    // correct values
      startSrc = 1;    // skip sign bit

      bigLen--;    // valid length of the string
    }

    int startDst = bitlen / 8 - bigLen;    //pad with leading nulls
    byte[] resizedBytes = new byte[bitlen / 8];

    System.arraycopy(bigBytes, startSrc, resizedBytes, startDst, bigLen);

    return resizedBytes;
  }

  /**
   * Method decodeBigIntegerFromElement
   *
   * @return the biginteger obtained from the node
   */
  public static final BigInteger decodeBigIntegerFromElement(Element element)
      throws Base64DecodingException {
    return new BigInteger(1, Base64.decode(element));
  }

  /**
   * Method decodeBigIntegerFromText
   *
   * @return the biginter obtained from the text node
   */
  public static final BigInteger decodeBigIntegerFromText(Text text)
      throws Base64DecodingException {
    return new BigInteger(1, Base64.decode(text.getData()));
  }

  /**
   * This method takes an (empty) Element and a BigInteger and adds the
   * base64 encoded BigInteger to the Element.
   */
  public static final void fillElementWithBigInteger(Element element, BigInteger biginteger) {

    String encodedInt = encode(biginteger);

    if (!XMLUtils.ignoreLineBreaks() && encodedInt.length() > BASE64DEFAULTLENGTH) {
      encodedInt = "\n" + encodedInt + "\n";
    }

    Document doc = element.getOwnerDocument();
    Text text = doc.createTextNode(encodedInt);

    element.appendChild(text);
  }

  /**
   * Method decode
   *
   * Takes the <CODE>Text</CODE> children of the Element and interprets
   * them as input for the <CODE>Base64.decode()</CODE> function.
   *
   * @return the byte obtained of the decoding the element $todo$ not tested yet
   */
  public static final byte[] decode(Element element) throws Base64DecodingException {

    Node sibling = element.getFirstChild();
    StringBuffer sb = new StringBuffer();

    while (sibling != null) {
      if (sibling.getNodeType() == Node.TEXT_NODE) {
        Text t = (Text) sibling;

        sb.append(t.getData());
      }
      sibling = sibling.getNextSibling();
    }

    return decode(sb.toString());
  }

  /**
   * Method encodeToElement
   *
   * @return an Element with the base64 encoded in the text.
   */
  public static final Element encodeToElement(Document doc, String localName, byte[] bytes) {
    Element el = XMLUtils.createElementInSignatureSpace(doc, localName);
    Text text = doc.createTextNode(encode(bytes));

    el.appendChild(text);

    return el;
  }

  /**
   * Method decode
   *
   * @return the UTF bytes of the base64
   */
  public static final byte[] decode(byte[] base64) throws Base64DecodingException {
    return decodeInternal(base64, -1);
  }

  /**
   * Encode a byte array and fold lines at the standard 76th character unless
   * ignore line breaks property is set.
   *
   * @param binaryData <code>byte[]<code> to be base64 encoded
   * @return the <code>String<code> with encoded data
   */
  public static final String encode(byte[] binaryData) {
    return XMLUtils.ignoreLineBreaks()
        ? encode(binaryData, Integer.MAX_VALUE)
        : encode(binaryData, BASE64DEFAULTLENGTH);
  }

  /**
   * Base64 decode the lines from the reader and return an InputStream
   * with the bytes.
   *
   * @return InputStream with the decoded bytes
   * @throws IOException passes what the reader throws
   */
  public static final byte[] decode(BufferedReader reader)
      throws IOException, Base64DecodingException {

    byte[] retBytes = null;
    UnsyncByteArrayOutputStream baos = null;
    try {
      baos = new UnsyncByteArrayOutputStream();
      String line;

      while (null != (line = reader.readLine())) {
        byte[] bytes = decode(line);
        baos.write(bytes);
      }
      retBytes = baos.toByteArray();
    } finally {
      baos.close();
    }

    return retBytes;
  }

  protected static final boolean isWhiteSpace(byte octect) {
    return (octect == 0x20 || octect == 0xd || octect == 0xa || octect == 0x9);
  }

  protected static final boolean isPad(byte octect) {
    return (octect == PAD);
  }

  /**
   * Encodes hex octets into Base64
   *
   * @param binaryData Array containing binaryData
   * @return Encoded Base64 array
   */
  /**
   * Encode a byte array in Base64 format and return an optionally
   * wrapped line.
   *
   * @param binaryData <code>byte[]</code> data to be encoded
   * @param length <code>int<code> length of wrapped lines; No wrapping if less than 4.
   * @return a <code>String</code> with encoded data
   */
  public static final String encode(byte[] binaryData, int length) {
    if (length < 4) {
      length = Integer.MAX_VALUE;
    }

    if (binaryData == null) {
      return null;
    }

    int lengthDataBits = binaryData.length * EIGHTBIT;
    if (lengthDataBits == 0) {
      return "";
    }

    int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
    int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
    int numberQuartet = fewerThan24bits != 0 ? numberTriplets + 1 : numberTriplets;
    int quartesPerLine = length / 4;
    int numberLines = (numberQuartet - 1) / quartesPerLine;
    char encodedData[] = null;

    encodedData = new char[numberQuartet * 4 + numberLines];

    byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;
    int encodedIndex = 0;
    int dataIndex = 0;
    int i = 0;

    for (int line = 0; line < numberLines; line++) {
      for (int quartet = 0; quartet < 19; quartet++) {
        b1 = binaryData[dataIndex++];
        b2 = binaryData[dataIndex++];
        b3 = binaryData[dataIndex++];

        l = (byte) (b2 & 0x0f);
        k = (byte) (b1 & 0x03);

        byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);

        byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
        byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);

        encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
        encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
        encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
        encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];

        i++;
      }
      encodedData[encodedIndex++] = 0xa;
    }

    for (; i < numberTriplets; i++) {
      b1 = binaryData[dataIndex++];
      b2 = binaryData[dataIndex++];
      b3 = binaryData[dataIndex++];

      l = (byte) (b2 & 0x0f);
      k = (byte) (b1 & 0x03);

      byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);

      byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
      byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);

      encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
      encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
      encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
      encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];
    }

    // form integral number of 6-bit groups
    if (fewerThan24bits == EIGHTBIT) {
      b1 = binaryData[dataIndex];
      k = (byte) (b1 & 0x03);
      byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
      encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
      encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];
      encodedData[encodedIndex++] = PAD;
      encodedData[encodedIndex++] = PAD;
    } else if (fewerThan24bits == SIXTEENBIT) {
      b1 = binaryData[dataIndex];
      b2 = binaryData[dataIndex + 1];
      l = (byte) (b2 & 0x0f);
      k = (byte) (b1 & 0x03);

      byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
      byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);

      encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
      encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
      encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];
      encodedData[encodedIndex++] = PAD;
    }

    //encodedData[encodedIndex] = 0xa;

    return new String(encodedData);
  }

  /**
   * Decodes Base64 data into octets
   *
   * @param encoded String containing base64 encoded data
   * @return byte array containing the decoded data
   * @throws Base64DecodingException if there is a problem decoding the data
   */
  public static final byte[] decode(String encoded) throws Base64DecodingException {
    if (encoded == null) {
      return null;
    }
    byte[] bytes = new byte[encoded.length()];
    int len = getBytesInternal(encoded, bytes);
    return decodeInternal(bytes, len);
  }

  protected static final int getBytesInternal(String s, byte[] result) {
    int length = s.length();

    int newSize = 0;
    for (int i = 0; i < length; i++) {
      byte dataS = (byte) s.charAt(i);
      if (!isWhiteSpace(dataS)) {
        result[newSize++] = dataS;
      }
    }
    return newSize;
  }

  protected static final byte[] decodeInternal(byte[] base64Data, int len)
      throws Base64DecodingException {
    // remove white spaces
    if (len == -1) {
      len = removeWhiteSpace(base64Data);
    }

    if (len % FOURBYTE != 0) {
      throw new Base64DecodingException("decoding.divisible.four");
      //should be divisible by four
    }

    int numberQuadruple = (len / FOURBYTE);

    if (numberQuadruple == 0) {
      return new byte[0];
    }

    byte decodedData[] = null;
    byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;

    int i = 0;
    int encodedIndex = 0;
    int dataIndex = 0;

    //decodedData = new byte[ (numberQuadruple)*3];
    dataIndex = (numberQuadruple - 1) * 4;
    encodedIndex = (numberQuadruple - 1) * 3;
    //first last bits.
    b1 = base64Alphabet[base64Data[dataIndex++]];
    b2 = base64Alphabet[base64Data[dataIndex++]];
    if ((b1 == -1) || (b2 == -1)) {
      //if found "no data" just return null
      throw new Base64DecodingException("decoding.general");
    }

    byte d3, d4;
    b3 = base64Alphabet[d3 = base64Data[dataIndex++]];
    b4 = base64Alphabet[d4 = base64Data[dataIndex++]];
    if ((b3 == -1) || (b4 == -1)) {
      //Check if they are PAD characters
      if (isPad(d3) && isPad(d4)) {               //Two PAD e.g. 3c[Pad][Pad]
        if ((b2 & 0xf) != 0) { //last 4 bits should be zero
          throw new Base64DecodingException("decoding.general");
        }
        decodedData = new byte[encodedIndex + 1];
        decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
      } else if (!isPad(d3) && isPad(d4)) {               //One PAD  e.g. 3cQ[Pad]
        if ((b3 & 0x3) != 0) { //last 2 bits should be zero
          throw new Base64DecodingException("decoding.general");
        }
        decodedData = new byte[encodedIndex + 2];
        decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
        decodedData[encodedIndex] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
      } else {
        //an error  like "3c[Pad]r", "3cdX", "3cXd", "3cXX" where X is non data
        throw new Base64DecodingException("decoding.general");
      }
    } else {
      //No PAD e.g 3cQl
      decodedData = new byte[encodedIndex + 3];
      decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
      decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
      decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
    }
    encodedIndex = 0;
    dataIndex = 0;
    //the begin
    for (i = numberQuadruple - 1; i > 0; i--) {
      b1 = base64Alphabet[base64Data[dataIndex++]];
      b2 = base64Alphabet[base64Data[dataIndex++]];
      b3 = base64Alphabet[base64Data[dataIndex++]];
      b4 = base64Alphabet[base64Data[dataIndex++]];

      if ((b1 == -1) ||
          (b2 == -1) ||
          (b3 == -1) ||
          (b4 == -1)) {
        //if found "no data" just return null
        throw new Base64DecodingException("decoding.general");
      }

      decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
      decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
      decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
    }
    return decodedData;
  }

  /**
   * Decodes Base64 data into outputstream
   *
   * @param base64Data String containing Base64 data
   * @param os the outputstream
   */
  public static final void decode(String base64Data, OutputStream os)
      throws Base64DecodingException, IOException {
    byte[] bytes = new byte[base64Data.length()];
    int len = getBytesInternal(base64Data, bytes);
    decode(bytes, os, len);
  }

  /**
   * Decodes Base64 data into outputstream
   *
   * @param base64Data Byte array containing Base64 data
   * @param os the outputstream
   */
  public static final void decode(byte[] base64Data, OutputStream os)
      throws Base64DecodingException, IOException {
    decode(base64Data, os, -1);
  }

  protected static final void decode(byte[] base64Data, OutputStream os, int len)
      throws Base64DecodingException, IOException {
    // remove white spaces
    if (len == -1) {
      len = removeWhiteSpace(base64Data);
    }

    if (len % FOURBYTE != 0) {
      throw new Base64DecodingException("decoding.divisible.four");
      //should be divisible by four
    }

    int numberQuadruple = (len / FOURBYTE);

    if (numberQuadruple == 0) {
      return;
    }

    //byte decodedData[] = null;
    byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;

    int i = 0;
    int dataIndex = 0;

    //the begin
    for (i = numberQuadruple - 1; i > 0; i--) {
      b1 = base64Alphabet[base64Data[dataIndex++]];
      b2 = base64Alphabet[base64Data[dataIndex++]];
      b3 = base64Alphabet[base64Data[dataIndex++]];
      b4 = base64Alphabet[base64Data[dataIndex++]];
      if ((b1 == -1) ||
          (b2 == -1) ||
          (b3 == -1) ||
          (b4 == -1)) {
        //if found "no data" just return null
        throw new Base64DecodingException("decoding.general");
      }

      os.write((byte) (b1 << 2 | b2 >> 4));
      os.write((byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf)));
      os.write((byte) (b3 << 6 | b4));
    }
    b1 = base64Alphabet[base64Data[dataIndex++]];
    b2 = base64Alphabet[base64Data[dataIndex++]];

    //  first last bits.
    if ((b1 == -1) || (b2 == -1)) {
      //if found "no data" just return null
      throw new Base64DecodingException("decoding.general");
    }

    byte d3, d4;
    b3 = base64Alphabet[d3 = base64Data[dataIndex++]];
    b4 = base64Alphabet[d4 = base64Data[dataIndex++]];
    if ((b3 == -1) || (b4 == -1)) { //Check if they are PAD characters
      if (isPad(d3) && isPad(d4)) {               //Two PAD e.g. 3c[Pad][Pad]
        if ((b2 & 0xf) != 0) { //last 4 bits should be zero
          throw new Base64DecodingException("decoding.general");
        }
        os.write((byte) (b1 << 2 | b2 >> 4));
      } else if (!isPad(d3) && isPad(d4)) {               //One PAD  e.g. 3cQ[Pad]
        if ((b3 & 0x3) != 0) { //last 2 bits should be zero
          throw new Base64DecodingException("decoding.general");
        }
        os.write((byte) (b1 << 2 | b2 >> 4));
        os.write((byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf)));
      } else {
        //an error  like "3c[Pad]r", "3cdX", "3cXd", "3cXX" where X is non data
        throw new Base64DecodingException("decoding.general");
      }
    } else {
      //No PAD e.g 3cQl
      os.write((byte) (b1 << 2 | b2 >> 4));
      os.write((byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf)));
      os.write((byte) (b3 << 6 | b4));
    }
  }

  /**
   * Decodes Base64 data into  outputstream
   *
   * @param is containing Base64 data
   * @param os the outputstream
   */
  public static final void decode(InputStream is, OutputStream os)
      throws Base64DecodingException, IOException {
    //byte decodedData[] = null;
    byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;

    int index = 0;
    byte[] data = new byte[4];
    int read;
    //the begin
    while ((read = is.read()) > 0) {
      byte readed = (byte) read;
      if (isWhiteSpace(readed)) {
        continue;
      }
      if (isPad(readed)) {
        data[index++] = readed;
        if (index == 3) {
          data[index++] = (byte) is.read();
        }
        break;
      }

      if ((data[index++] = readed) == -1) {
        //if found "no data" just return null
        throw new Base64DecodingException("decoding.general");
      }

      if (index != 4) {
        continue;
      }
      index = 0;
      b1 = base64Alphabet[data[0]];
      b2 = base64Alphabet[data[1]];
      b3 = base64Alphabet[data[2]];
      b4 = base64Alphabet[data[3]];

      os.write((byte) (b1 << 2 | b2 >> 4));
      os.write((byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf)));
      os.write((byte) (b3 << 6 | b4));
    }

    byte d1 = data[0], d2 = data[1], d3 = data[2], d4 = data[3];
    b1 = base64Alphabet[d1];
    b2 = base64Alphabet[d2];
    b3 = base64Alphabet[d3];
    b4 = base64Alphabet[d4];
    if ((b3 == -1) || (b4 == -1)) { //Check if they are PAD characters
      if (isPad(d3) && isPad(d4)) {               //Two PAD e.g. 3c[Pad][Pad]
        if ((b2 & 0xf) != 0) { //last 4 bits should be zero
          throw new Base64DecodingException("decoding.general");
        }
        os.write((byte) (b1 << 2 | b2 >> 4));
      } else if (!isPad(d3) && isPad(d4)) {               //One PAD  e.g. 3cQ[Pad]
        b3 = base64Alphabet[d3];
        if ((b3 & 0x3) != 0) { //last 2 bits should be zero
          throw new Base64DecodingException("decoding.general");
        }
        os.write((byte) (b1 << 2 | b2 >> 4));
        os.write((byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf)));
      } else {
        //an error  like "3c[Pad]r", "3cdX", "3cXd", "3cXX" where X is non data
        throw new Base64DecodingException("decoding.general");
      }
    } else {
      //No PAD e.g 3cQl
      os.write((byte) (b1 << 2 | b2 >> 4));
      os.write((byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf)));
      os.write((byte) (b3 << 6 | b4));
    }
  }

  /**
   * remove WhiteSpace from MIME containing encoded Base64 data.
   *
   * @param data the byte array of base64 data (with WS)
   * @return the new length
   */
  protected static final int removeWhiteSpace(byte[] data) {
    if (data == null) {
      return 0;
    }

    // count characters that's not whitespace
    int newSize = 0;
    int len = data.length;
    for (int i = 0; i < len; i++) {
      byte dataS = data[i];
      if (!isWhiteSpace(dataS)) {
        data[newSize++] = dataS;
      }
    }
    return newSize;
  }
}
